Ignition system



' Wm HTTOIFNEYS Patented June 28, 1949 IGNITION SYSTEM Brooks H. Short and Herman L. Hartzell, Anderson, Ind., assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application September 19, 1947, Serial No. 774,908

6 Claims. 3

This invention relates to ignition systems for internal combustion engines, particularly the type of system in which ignition energy is provided by the discharging of a condenser which is charged by a suitable current source. The discharge of the condenser is under control by-thyratron which is normally nonconducting but which becomes conducting when an auxiliary condenser discharges through the grid of the thyratron. In the copending application of Short and Tynan, Serial No. 611,402, filed August 18, 1945, now Patent No. 2,463,123, issued March 1, 1949, there is disclosed an engine driven ignition timer for controlling the discharge of the auxiliary condenser to the grid of the thyratron. The variations in ignition timing in response to engine operating conditions, such as speed and load, would be efiected by the use of a conventional timer having speed responsive means for varying angular relation of the timer cam and the engine driven shaft which drives it and having means responsive to manifold vacuum for varying the positionof the circuit breaker lever relative to the timer cam.

An object of the present invention is to provide means under the control of the engine and effected by variations in speed and engine load for varying'the timing of the ignition in a system of the type referred to but without resorting to the use of a timer having make and break 4 contacts. In the disclosed embodiment of the invention, this object is accomplished by the use of a pick-up coil in which a voltage is induced by a permanent magnet driven by the engine. The pick-up coil islocated far enough in advance of top dead center to take care of all possible advance requirements. The energization of the pick-up c'oil determines the beginning of the! char ing of the auxiliary condenser. The variations in the ignition timing are effected by vary ing the extent of the time required to bring the auxiliary condenser up to such state of charge that it has sufficient potential to render the thyratron conducting. The variation of the extent of time for charging the auxiliary condenser up .tothe required potential is efiected by variable The figure of the drawing is a diagram of an embodiment of the invention.

In the drawing, power supplying wires are designated by numerals i6 and ii. Wire it is connected through resistance it with a main condenser or capacitor is and the primary I! of an ignition coil l8 having a secondary it which is connected with an ignition distributor, not shown. Wire 20 connects primary it with wire it. Thus, the main condenser i6 is charged. The discharge of the main condenser it is withheld by thyratron 2i, filled preferably with hydrogen and having a plate 22, a grid 23 and a cathode 24 having a heater, not shown. Grid 23 is connected with an auxiliary condenser or capacitor 25 connected with wire it. Wire 26 is connected with wire it and with an arm 2i carrying a contact or wiper as moving as indicated by are 29 upon the face of a resistance bar 33. Bar 30 is contacted by another wiper 32 moving in the path of arc 3i and carried by an arm 33 connected with a wire 3t which is connected to the plate 36 of a thyratron 35 also filled with hydrogen. Thyratron 35 has a grid 31 and a cathode 38 having a heater, not shown. Grid 31 and cathode 38 are connected with a pick-up coil 40 surrounding one leg of a U-shaped core 4|, the poles of which face toward a permanent magnet bar 42 carried by a disc such as the flywheel 43 driven by the engine. The parts 40, 4| and 42 constitute an engine operated magneto generator. The number of magnets 42 depends on the number of cylinders of the engine. For example, in a ,four-cycle engine having eight cylinders, the flywheel would carry four magnets 42. The location of the core 4|, and hence the pick-up coil 40, is located far enough in advance of top dead center to take care of all possible advance requirements of the timing ignition.

The operation of the system is as follows: During the rotation of the disc 43 the capacitor I6 is charged through the resistor IE to full voltage and the capacitor 25 is uncharged before the magnet segment is in alignment with pick-up coil core 4].. When the magnet segment 42 is in alignment with the pick-up core 4|, a voltage is generated in winding 40 that is applied to the grid 31 of the thyratron tube 35 and causes the tube to be conducting. At this instant the con-; denser or capacitor 25 is then charged through the, resistance of bar element 30 and througlt the plate 36 and cathode 38 of thyratron tube I 35, at a rate determined by the resistance of the element 30. When the voltage across the con denser reaches a critical value for firing the grid 23 of thyratron tube 2|, the tube becomes ionized and the condenser or capacitor is discharges through the plate 22 to cathode 24 of tube 2| and then through primary l1 of ignition coil l5. This discharge is stepped up in the secondary Is to ignition magnitude. The capacitor continues to discharge until its voltage drops to a very low value, thus allowing both thyratron tubes 55, 2| to deionize as the capacitor 25 was discharged by the grid 23 at the time of its ionization. Following this series of conditions the capacitor is is again charged through the resistance i5 and the entire circuit is again conditioned for the next impulse. Since the pick-up coil causes the thyratron 35 to be conducting at the same instant or instants during each revolution, it is apparent that the beginning of the charging of the condenser 25 will not vary with respect to the angular position or the flywheel 43. The variation in the ignition timing is dependent upon the time required to so charge the condenser 25 that the potential as applied to the grid 23 is suflicient to cause the thyratron 35 to become conducting. The time of the conducting of condenser 25 depends on the relative position of the wipers 28 and 32. When these wipers are closetogether the time for charging the condenser 25 with the required potential will be less than when the wipers are further apart.

Wiper 28 is under control by engine intake vacuum which is communicated through pipe 50 to a chamber 5| closed We fixed wall 52 and a diaphragm 53 urged away from the fixed wall by a spring 54 Diaphragm 53 is connected with a rod 55 having a rack 55 meshing with a gear 51 the condenser to the critical value will be longer. Therefore, the timing of the ignition will be retarded. The apparatus responds to various combinations of speed and load to vary the time of increase of voltage of condenser 25 to the value required to render the thyratron conducting. Hence the timing of ignition is advanced or retarded to suit engine operating conditions. Whilethe embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Ignition apparatus for internal combustion engines comprising an ignition coil, a current source, a main condenser charged thereby, a thyratron for withholding discharge of the main condenser'to the coil until the desired instant of ignition, an auxiliary condenser connected with the grid of the thyratron to cause the thyratron to become conducting when the'auxiliary condenser attains a potential sufilcient for discharge which carries the wiper arm- 21. When intake vacuum is high, wiper will move toward position H and when intake vacuum is low, wiper-will move toward position L.

Wiper 32 is under control by engine speed. For this purpose an engine driven shaft 50 is connected by a gearGl with a gear 52 journaled in a. bearing and carrying lugs 54 carrying pins 55 pivotally supporting weighted bell crank levers 65 Levers 55 engage the under race of a thrust bearing 51, the upper race of which is connected with a rod 55 having a rack. 59 meshing with a gear 10 meshing with a gear 1| which carries the arm 33. Centrifugal force ailecting levers 55 is opposed by spring 12 confined between the upper end of rod 58 and a retainer cup 12 which can be adjusted vertically by screw 14 threaded through a stationary part 15 and retively low, the wipers 32 and" will be located,.

respectively, near the F and H marks. Since the amount ofresistance included between the wiper is relatively low, the time required for rise inpotential oi the condenser 25 to'that required for rendering the thyratron conducting will be relatively short, and the timing of the ignition will be advanced. When the speed is low and the engine load is high, the wipers will be nearer to S and L, respectively. Hence the e'flective value of the resistance 30 will be higher, and

the time required for raisingthe potential of to said grid, means controlled by the engine for efiecting a connection between the current source and the auxiliary condenser, a variable resistance in the charging circuit of the auxiliary condenser, and means responsive to engine operating conditions for controlling the variable resistance.

2-. Ignition apparatus for internal combustion engines comprising an ignition coil, a current source, a main condenser charged thereby, a thyratron for withholding discharge of the main condenser to the coil until the desired instant of ignition, an auxiliary condenser connected with the grid of the thyratron to cause the thyratron to become conducting. when the auxiliary condenser attains a potential sufficient for discharge to said grid, means controlled by the engine for efiecting a connection between the current source and the auxiliary condenser, a variable resistance in the charging circuit of the auxiliary condenser, and means responsive to engine speed for controlling the variable resistance to lower the resistance in the charging circuit of the auxiliary condenser as speed increases.

3. Ignition apparatus for internal combustion engines comprising an ignition coil, a current source, a main condenser charged thereby, a thyratron for withholding discharge oi the main condenser to the coil until the desiredinstant of ignition, an auxiliary condenser connected with the grid of the thyratron to cause the thyratron to become conducting when the auxiliary condenser attains a potential sufilcient for discharge to said grid. means controlled by the engine for effecting a connection between the current source and the auxiliary condenser, a

7 variable resistance in the charging circuit of the auxiliary condenser, and means responsive to engine intake suction for controlling the variable ignition, an auxiliary condenser connected withthe grid of the thyratron to cause the thyratron to become conducting when the auxiliary condenser attains a potential sufllcient for discharge to said grid, means controlled by the engine for efiecting a connection between the current source and the auxiliary condenser, a resistance element in the charging circuit of the auxiliary condenser, two wipers for traversing the element, means for controlling the position of one of the wipers in accordance with engine speed, and means for controlling the position of the other wiper in accordance with engine intake suction.

. 5. Ignition apparatus 'for internal combustion engines comprising an ignition coil, a current source, a main condenser. charged thereby, a thyratron for withholding discharge of the main condenser to the coil until the desired instant of ignition, an auxiliary condenser connected with the grid of the thyratron to cause the thyratron to become conducting when the auxiliary con-. denser attains a potential suflicient for discharge to said grid, a circuit for connecting the auxiliary condenser with'the current source and including a second thyratron and a variable resistance, a magneto generator operated by the engine and having a coil connected with the grid of the second thyratron to render said thyratron conducting whereby the charging of the auxiliary condenser begins at a certain instant in the operation of the engine, and means responsive to engine operating conditions for controlling the variable resistance in order to vary the duration of potential increase at the auxiliary condenser to a value suflicient to cause the first thyratron to become conducting.

6. Ignition apparatus for internal combustion engines comprising an ignition coil, a current source, a main condenser charged thereby, an auxiliary condenser, means rendered effective to connect the main condenser with the ignition coil Y for discharge of said condenser when the potential at the auxiliary condenser attains a certain value, a circuit for connecting the auxiliary condenser with the current source and including a thyratron and a variable resistance, a magneto generator operated 'by the engine and having a' coil connected with the grid of the thyratron to cause it to become conducting at a certain instant in the operation of the engine, and means REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,175,900 Knight Oct, 10, 1939 2,353,527 'I'ouceda et al. July 11, 1944 

